As the above-described valve opening/closing timing control device, JP 2015-78635A (Reference 1) discloses a technology in which a spool is coaxially disposed with a rotation axis, a relative rotation phase is controlled in an advance direction and a retard direction by operating the spool in a direction along the rotation axis, and thus, a lock mechanism is shifted to a locked state by setting the spool to an operation end in the advance direction and an operation end in the retard direction.
In Reference 1, a drain flow path (a main discharge flow path in Reference 1) is formed inside the spool and a fluid discharged from an advance flow path and a retard flow path and a fluid discharged from the lock mechanism are discharged from the drain flow path.
As described in Reference 1, the single spool is coaxially provided with the rotation axis of the valve opening/closing timing control device and the fluid is discharged from the drain flow path inside the spool. Accordingly, for example, in a case where the fluid is supplied to an advance chamber by operating the spool and the state is shifted to the locked state, the fluid flows from a retard chamber to the drain flow path and the fluid from an unlocking flow path flows to the drain flow path.
In Reference 1, the drain flow path having a relatively large flow path cross-sectional area is provided inside the spool. However, even when the drain flow path having a large diameter is provided, in a case where the drain of the drain flow path cannot catch up drainage capacity, a pressure in the drain flow path increases. In addition, the valve opening/closing timing control device and the spool rotate at a high speed during an operation of an internal combustion engine, and thus, in the drain flow path, the fluid is pressed to an inner peripheral wall of the spool by a centrifugal force and the pressure of the fluid in the drain flow path increases. Accordingly, in the configuration in which the unlocking flow path is combined to the drain flow path, the flow of the combined fluid is obstructed, and as a result, unlocking cannot be appropriately performed.
Particularly, when a fluid is supplied to the advance chamber, a pressure acts on a fluid discharged from the retard chamber according to the supply, but only a pressure caused by an urging force of a spring applied to a lock member acts on the fluid discharged from a lock flow path during locking. Accordingly, the pressure decreases during discharging of the fluid, and in a case where the flow of the fluid is obstructed, shifting of the lock mechanism to the locked state may not be appropriately performed.
Here, difficulty of shifting to the locked state peculiar to an intermediate lock will be described. For example, in the most retarded lock or the most advanced lock, lock shifting can be performed in a state where a vane abuts on a wall portion and a phase stops. Compared to this configuration, in a configuration which includes a lock phase other than the most advance phase or the most retard phase, when the state is shifted to a locked state, it is required to be rapidly shifted to the locked state when a lock member and a lock recessed portion reach a phase capable of engaging with each other in a situation where the lock member and the lock recessed portion are always displaced relative to each other. Accordingly, from this reason, the shifting to the locked state is difficult.
This disadvantage is remarkable in a case where, in a configuration in which engine oil is used as a fluid in a vehicle, the temperature of the fluid is low and the viscosity of the fluid is high such as immediately after the engine starts in a low-temperature environment.
In order to prevent the inappropriate operation, for example, it is considered that a phase control hydraulic valve for controlling a working oil supplied to or discharged from an advance chamber and a retard chamber and a lock control hydraulic valve for controlling a lock mechanism are provided. In this configuration, by opening a phase control fluid valve in a state where a fluid is discharged from the lock control hydraulic valve, the state can be reliably shifted to the locked state at the timing when the relative rotation phase reaches the lock phase.
However, in this configuration, the two hydraulic valves are required, and thus, the number of parts increases, an oil passage configuration is complicated, and a size of the configuration increases.
Thus, a need exists for a valve opening/closing timing control device which is not susceptible to the drawback mentioned above.